1. Field of the Invention
The invention relates in general to an apparatus and method for switching audio amplification, and more particularly to an apparatus and method for switching audio amplification with multi-level pulse width modulation.
2. Description of the Related Art
A Class D amplifier or switching amplifier is an electronic amplifier where all power devices (usually MOSFETs) are operated as binary switches, thus significantly reducing the power losses and achieving high efficiencies. A conventional class D amplifier drives a speaker according to a pulse width modulated (PWM) waveform switching between a voltage level (VDD) and ground. Such switching of voltage level is likened to square wave operation and thus leads to electro-magnetic interference (EMI) problem. The class D amplifier conventionally includes a filter such as a LC filter or low pass filter to filter out the undesirable harmonics in order to reduce the EMI noise. However, the inclusion of filter will inevitably increase the total cost and result in a larger chip size which will occupy larger area on the printed circuit board on which the class D amplifier is disposed.